‘Nothing fishy’ about huge carp die-off

By Zenzile Khoisan Time of article published Mar 5, 2016

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MORE than 15 tons of stinking carp, which apparently died of natural causes, are being removed from Zeekoevlei by the City of Cape Town’s biodiversity unit.

City officials launched the huge removal operation after more than 5 000 fish, all of the same sensitive freshwater species, began popping to the surface of the vlei en masse in an area at the confluence of the Lotus River and the Zeekoevlei waterway.

In the face of a large social media outcry, with people raising fears of large-scale poisoning of the fish, officials said the event could not be attributed to sewage or other toxic substances being introduced into the marine enclave.

Asieff Khan, area manager for the False Bay Nature Reserve’s Environmental Resource Management department, said they could also confirm the large carp “die-off” had not affected other parts of the vlei.

A significant number of the dead fish had been removed by late afternoon.

“Our officials and staff have been busy since (yesterday) morning and so far we have removed approximately seven tons of an estimated 15 tons of dead fish from the Lotus River area of Zeekoevlei.”

After examination, they believed the large number of dead fish could be attributed to a combination of low water levels, higher temperatures, decomposing algae bloom and the carp herpes virus.

Another contributing factor was that there was little water movement in and around the confluence of the Lotus River and Zeekoevlei.

Khan said while alarming, the death of fish due to these factors was a natural event. There had been four such occurrences in the past two years.

A clear indication the deaths were not the result of a large amount of sewage leaking into the waterway was that this event had affected only carp and the fish deaths were isolated to a specific area.

“If we were dealing with sewage leaking into the vlei, it would have affected all other species, which in this instance has not been the case.”

He urged people not to go to the area and not to eat the fish, which were not safe for human consumption.

“There is a massive stench over the place, which is because the fish only surface, bloated with gases, two days after they die. When they pop to the surface the fish are slimy and possess an unpleasant smell, so our message to everyone is clear, do not eat this fish, because it is not fit for human consumption,” Khan said.

The biodiversity unit had been assisted by the sanitation department to remove the fish to the city’s waste disposal site at Vissershok.

The City of Cape Town said in a statement yesterday the death of such a large number of carp was classified as a “fish kill”.

“Fish kills, which refer to a localised die-off of fish populations, often occur at this time of the year with the change of seasons when water levels are low and temperatures are high.

“Fish sometimes become stressed during breeding and they may pass on infectious diseases due to the grouping of large numbers of adult fish together.”

The official statement said tests had been conducted to ascertain the cause but natural causes were suspected.

“Lab results today of samples taken yesterday indicate low traces of algal toxins well below the guideline limits in the affected area. Samples taken this afternoon indicate no toxins present in the affected area.”

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